Magnetic resonance imaging (MRI) techniques provide multidimensional images of soft tissues of the body. This non-invasive procedure is conducted on live animals and current technology permits volume resolution of 20 x 20 x 50 microns. Thus, it is possible to perform microscopy on live animals utilizing MRI techniques developed by Dr. G. Allan Johnson of Duke University. Collaborative studies conducted to date have demonstrated the utility of following progression and regression of toxic lesions in the kidney and liver of chemically treated rats. Current work is focused on development of imaging strategies to characterize specific types of lesions induced by several target organ toxicants to provide an adjunct to conventional pathologic studies and, at the same time, avoid the necessity for use of large numbers of experimental animals in toxicity studies. Collaborative studies will continue for the next year.